Methane and nitrous oxide fluxes in relation to vegetation covers and bird activity in ice-free soils of Rip Point, Nelson Island, Antarctica

Abstract

This study aimed to quantify the nitrous oxide (N₂O) and methane (CH₄) fluxes at sites with different vegetation covers and where bird activity was present or absent using the static chamber method, on Rip Point, Nelson Island, maritime Antarctic. The sites were soils covered by Sanionia uncinata, lichens, Prasiola crispa, Deschampsia antarctica and bare soil. Seabirds used the P. crispa and D. antarctica sites as nesting areas. Soil mineral N contents, air and soil temperature and water-filled pore space were measured, and the content of total organic C and particulate organic C, total N, bulk density and texture were determined to identify controlling variables of the gas emissions. The N₂O and CH₄ flux rates were low for all sampling events. Mean N₂O flux rates ranged from 0.11±1.93 up to 21.25±22.14 µg N₂O m⁻² h⁻¹ for the soils under lichen and P. crispa cover, respectively. For the CH₄ fluxes, only the P. crispa site showed a low positive mean (0.47±3.61 µg CH₄ m⁻² h⁻¹). The bare soil showed the greatest absorption of CH₄ (−11.92±5.7 µg CH₄ m⁻² h⁻¹), probably favoured by the coarse soil texture. Bare soil and S. uncinata sites had N₂O accumulated emissions close to zero. Net CH₄ accumulated emission was observed only at the P. crispa site, which was correlated with (p<0.001). These results indicate that seabird activity influences N₂O and CH₄ soil fluxes, while vegetation has little influence, and bare soil areas in maritime Antarctica could be greenhouse gas sinks.

• Soil greenhouse gases
• seabirds
• vegetal cover
• maritime Antarctica.

Acknowledgements

This work was supported by the Brazilian Antarctic Program through the Brazilian Council for Scientific and Technologic Development, Foundation of Research Support in Rio de Janeiro, Foundation of Research Support in Rio Grande do Sul, Ministry of Environment, Ministry of Science and Technology and Innovation and the Interministerial Commission for the Sea Resources, through the National Institute of Science and Technology—Antarctic Environmental Research.